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为了更好满足地震计的振动测试需求,对振动台的波形失真度、横向运动比、台面不均匀度及稳定性等主要性能指标进行了测试分析.测试结果表明:该振动台具有较好的低频振动特性.利用低频标准套组对该振动台和中国计量科学研究院标准振动台进行比对分析,测试结果存在较小偏差. 相似文献
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校准是保证传感器测量数据准确的前提。低频振动传感器在地震观测、土木水利与建筑工程、机械与运载工程、能源与矿业工程等领域愈来愈获得广泛应用。这些传感器都需要在低频振动标准装置上进行校准,而低频标准振动台是低频振动标准装置的关键设备,低频标准振动台的设计和制造技术通常决定了一个国家低频振动校准的水平。振动台在校准中用于产生标准振动信号,通常情况下是正弦信号,但校准激励信号有从稳态正弦信号向随机信号发展的趋势。目前,低频振动传感器的校准通常是在实验室进行的,但是一些在线监测系统对传感器的现场校准提出了要求。本文重点研究了以下3方面内容:(1)低频标准振动台的控制技术。建立了低频标准振动台的数学模型,并实际设计了一种便携式的低频标准振动台,对设计的低频振动台进行了测试。测试结果表明,该振动台加速度信号可以低至0.5Hz,速度信号可以低至0.1 Hz,能够满足一般低频振动传感器的校准需要,可满足省一级的计量机构、振动传感器生产商以及大量使用低频振动传感器单位的校准需求。(2)对以地震波作为激励信号的校准方法进行了研究。探索了在低频标准振动台上产生地震波的方法,在中国地震局工程力学研究所的低频标准振动台上实现了地震波复现,大部分情况下复现的地震波与原始地震波记录的相关系数可以达到0.95以上。随后以地震波作为校准激励信号,对传感器进行了校准,将校准结果与激光干涉法振动绝对校准方法的校准结果进行了比较,获得了理想的结果。(3)对振动传感器的现场校准方法进行了探讨。虽然以往自标定(校准)方法一直在使用,但并未对系统进行详细的分析研究。本文针对4种类型的内置校准线圈传感器,分别利用自校准方法和激光干涉法振动绝对校准方法进行校准。2种校准方法的校准结果表明,低频段(10Hz以下)结果一致,高频段有偏差。以无源伺服式振动传感器为例,对自校准下的传感器数学关系进行了系统的分析,自校准时的反感应电动势、感抗(自感和互感)是造成这种偏差的原因。本文第一章阐述文章的背景,第二、三、四、五章是文章的主体,对本文重点研究的问题进行了阐述。第六章对未来的工作进行了展望,提出了低频标准振动台的发展方向和实用的现场校准系统实现的方法。 相似文献
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宽频带超低频标准振动台的研究 总被引：1，自引：1，他引：0
主要介绍了为中国地震局工程力学研究所振动计量实验室的技术升级项目研制的垂直和水平超低频振动台.水平振动台采用单导轨结构,大大提高了振动位移,达150mm(p-p),同时加宽了使用频率范围,可从0.01～250Hz ,而且加工、安装、调试、维护都十分方便.振动台取消了机械弹簧,代之以自动控制电弹簧,比原振动台的超低频性能大为改善,在控制方面,采用相对速度与绝对速度复合反馈技术.振动台的波形失真度,振级稳定性、横向振动比、低频背景噪声等各项技术指标达到或超过国际标准,为低频、超低频振动传感器的检定提供更精更准确的检定装置. 相似文献
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大型振动离心机设备设计关键技术研究 总被引：4，自引：1，他引：3
大型振动离心机作为代表岩土地震工程最高试验技术水平的新型尖端试验设备,目前全球仪有美国和日本各1台,而我国目前为空白,与我国严峻的地震形势、复杂的工程地质环境与高速发展的工程建设不相匹配.文中概述了国际大型振动离心机建设现状,通过跟踪现有两台大型振动离心机技术发展,分析比较了优缺点,研究了大型振动离心机设备设计关键技术.分析表明,振动台的振动容量和振动负载为振动离心机的核心技术指标,振动台为大型振动离心机建设是否成功的关键;振动台设计的核心是电液伺服激振系统,决定了振动台的总体运行性能;振动台设计的要点是台体和动力源,分别决定着系统支承和动力的性能;离心机和振动台之间相互影响和制约,多种因素需要协调考虑.同时,文中对其中部分问题提出了解决对策和建议,可为国内大型振动离心机设备设计提供帮助和参考. 相似文献
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上海环球金融中心大厦整体结构振动台试验设计 总被引：11，自引：2，他引：11
同济大学土木工程防灾国家重点实验室对上海环球金融中心大厦进行了整体结构模型的振动台试验.该大厦101层,结构高度492m,拟建成为世界上结构主体最高的建筑物.本文详细介绍了大厦结构体系、振动台试验模型材料的选取、动力相似关系的确定以及试验方案的设计.针对超高层整体结构小比例模型施工困难的特点,提出了模型的简化方法,并利用ANSYS对简化模型进行了计算,计算结果表明模型简化对结构自振特性和地震反应影响很小,验证了简化方法的可行性.本文提供的模型和试验的设计思路对今后有关的试验工作有一定的借鉴作用. 相似文献
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为了避免福岭采石场爆破施工对周边民房的影响,布设4个测试点,对不同药量及距离产生的爆破振动给附近民房带来的影响进行监测和分析,得到了振动衰减关系及该采石场爆破施工对附近民房影响的安全距离。当保护对象距离为200 m时,96 kg药量,振动速度为0.45 cm/s,达到土坯房和毛石房屋容许振动的上限值。 相似文献
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应泽成 《地震地磁观测与研究》1985,(4)
波形的非线性失真度是评定振动台运动精度的一项重要技术指标,而目前国内外还没有直接测量波形频率低于2Hz的失真度仪,这就限制了低频标准振动台的使用范围,而这正是地震系统及其它一些低频测振系统共同关心的部分。本文提出的超低频波形失真度测量法,是应用FFT方法在频域上展示并量取各次谐波幅值,通过简单计算得出超低频失真度量值。我们已用该方法对中国计量科学院生产的垂直向低频标准振动台和水平向振动台作了频率低于2Hz的失真度量值测试,并获得结果。在国内首次扩大了该套振动装置的使用频率下限,为地震仪及低频测振仪的标定工作作出了贡献。该方法也适用于其它如机电转换装置及电信号发生、记录、转换装置的失真度量值测试。 相似文献
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对振动台在大行程移动过程中导轨不平顺引起的倾斜效应进行了理论分析，选择0.1 Hz及以下频点开展振动台导轨不平顺引起的台面倾斜对测试结果影响的定量化分析。结果表明，振动台面在移动过程中的不确定倾斜对地震计水平分量灵敏度的影响大于对垂直分量灵敏度的影响。采用高精度水平仪获取水平振动台在不同行程下的运动轨迹起伏变化，并基于倾斜效应的影响机制，用Labview语言实现补偿系统，在地震计的振动测试中对测试结果进行动态补偿。测试结果表明，经过动态补偿，导轨不平顺不再对灵敏度校准结果存在明显制约，可大幅提高地震计的低频测试精度。 相似文献
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Dynamic characteristics and seismic behavior of prefabricated steel stairs in a full‐scale five‐story building shake table test program 
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下载免费PDF全文 Xiang Wang Rodrigo Astroza Tara C. Hutchinson Joel P. Conte José I. Restrepo 《地震工程与结构动力学》2015,44(14):2507-2527
This paper investigates the dynamic characteristics and seismic behavior of prefabricated steel stairs in a full‐scale five‐story building shake table test program. The test building was subjected to a suite of earthquake input motions and low‐amplitude white noise base excitations first, while the building was isolated at its base, and subsequently while it was fixed to the shake table platen. This paper presents the modal characteristics of the stairs identified using the data recorded from white noise base excitation tests as well as the physical and measured responses of the stairs from the earthquake tests. The observed damage to the stairs is categorized into three distinct damage states and is correlated with the interstory drift demands of the building. These shake table tests highlight the seismic vulnerability of modern designed stair systems and in particular identifies as a key research need the importance of improving the deformability of flight‐to‐building connections. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Xiang Wang Tara C. Hutchinson Rodrigo Astroza Joel P. Conte José I. Restrepo Matthew S. Hoehler Waldir Ribeiro 《地震工程与结构动力学》2017,46(3):391-407
This paper investigates the seismic performance of a functional traction elevator as part of a full‐scale five‐story building shake table test program. The test building was subjected to a suite of earthquake input motions of increasing intensity, first while the building was isolated at its base and subsequently while it was fixed to the shake table platen. In addition, low‐amplitude white noise base excitation tests were conducted while the elevator system was placed in three different configurations, namely, by varying the vertical location of its cabin and counterweight, to study the acceleration amplifications of the elevator components due to dynamic excitations. During the earthquake tests, detailed observation of the physical damage and operability of the elevator as well as its measured response are reported. Although the cabin and counterweight sustained large accelerations because of impact during these tests, the use of well‐restrained guide shoes demonstrated its effectiveness in preventing the cabin and counterweight from derailment during high‐intensity earthquake shaking. However, differential displacements induced by the building imposed undesirable distortion of the elevator components and their surrounding support structure, which caused damage and inoperability of the elevator doors. It is recommended that these aspects be explicitly considered in elevator seismic design. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Large‐scale, servo‐hydraulic shake tables are a central fixture of many earthquake engineering and structural dynamics laboratories. Wear and component failure from frequent use may lead to control problems resulting in reduced motion fidelity, necessitating repairs and replacement of major components. This paper presents a methodology to evaluate shake table performance pre‐ and post‐repair, including the definition of important performance metrics. The strategy suggested is presented in the context of the rebuilding of a 4.9 × 3.1 m, 350‐kN‐capacity uniaxial shake table. In this case, the rebuild consisted of characterization of wear to table components, replacement of worn bearing surfaces, and replacement of hydraulic accumulators. To assess the effectiveness of the repair actions, sinusoidal and triangular waves, white noise, and earthquake histories were run on the table before and after the rebuild. The repair actions were successful in reducing the position and velocity dependence of friction, improving the ability of control algorithms to accurately reproduce earthquake motions. The maximum and average response spectral misfits in the period range of 0.1–2 seconds were reduced from approximately 50% to 15%, and from 5% to less than 2.5%, respectively. 相似文献
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This paper presents results of a comprehensive experimental program on the seismic response of full‐scale freestanding laboratory equipment. First, quasi‐static experiments are conducted to examine the mechanical behavior of the contact interface between the laboratory equipment and floors. Based on the experimental results, the response analysis that follows adopts two idealized contact friction models: the elastoplastic model and the classical Coulomb friction model. Subsequently, the paper presents shake table test results of full‐scale freestanding equipment subjected to ground and floor motions of hazard levels with corresponding displacements that can be accommodated by the shake table at the UC Berkeley Earthquake Engineering Research Center. For the equipment tested, although some rocking is observed, sliding is the predominant mode of response, with sliding displacements reaching up to 60 cm. Numerical simulations with the proposed models are performed. Finally, the paper identifies a physically motivated intensity measure and the associated engineering demand parameter with the help of dimensional analysis and presents ready‐to‐use fragility curves. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Shake tables provide a direct means by which to evaluate structural performance under earthquake excitation. Because the entire structure is mounted on the base plate and subjected to the ground motion in real time, dynamic effects and rate‐dependent behavior can be accurately represented. Shake table control is not straightforward as the desired signal is an acceleration record, while most actuators operate in displacement feedback for stability. At the same time, the payload is typically large relative to the capacity of the actuator, leading to pronounced control‐structure interaction. Through this interaction, the dynamics of the specimen influence the dynamics of the shake table, which can be problematic when specimens change behavior because of damage or other nonlinearities. Moreover, shake tables are themselves inherently nonlinear, making it difficult to accurately recreate a desired acceleration record over a broad range of amplitudes and frequencies. A model‐based multi‐metric shake table control strategy is proposed to improve tracking of the desired acceleration of a uniaxial shake table, remaining robust to nonlinearities including changes in specimen condition. The proposed strategy is verified for the shake table testing of both linear and nonlinear structures. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Among several different experimental techniques, used to test the response of structures and to verify their seismic performance, the shake table testing allows to reproduce the conditions of true effects of earthquake ground motions in order to challenge complex model structures and systems. However, the reproduction of dynamic signals, due to the dynamics of the shake table and of the specimen, is usually imperfect even though closed‐loop control in a shake table system is used to reduce these errors and obtain the best fidelity reproduction. Furthermore, because of the dynamic amplifications in the specimen, the signal recorded at desired locations could be completely different from the expected effect of shake table motion. This paper focuses on the development of practical shake table simulations using additional ‘open loop’ feedforward compensation in form of inverse transfer functions (i.e. the ratio of the output structural response to an input base motion in the frequency domain) in order to obtain an acceptable reproduction of desired acceleration histories at specific locations in the specimen. As the first step, a well‐known global feedforward procedure is reformulated for the compensation of the table motion distortions due to the servo‐hydraulic system. Subsequently, the same concept is extended to the table‐structure system to adjust the shake table input in order to achieve a desired response spectrum at any floor of the specimen. Implementations show how such a method can be used in any experimental facility. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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笔者提出使用对比法测试地震计传感参数,即灵敏度、敏感轴方向角和倾角等的方案,包括测试数据采集、测试频带选择、传感参数计算方法等,并给出参数结果误差估计方法。为了满足斜轴悬挂、UVW输出地震计参数测试需要,给出此类地震计传感参数测试方案。通过合成数据、振动台检验验证,批量地震计参数重复测试证明该测试方法精度高、可信、可靠。对比法既适用于大批量地震仪器参数测试,也适用于地震台站现场,在不影响台站日常观测情况下,对单个地震计参数进行测试,其测试条件要求不高,操作简单、快捷,是测试生产、观测中地震计传感参数的一种可行办法。 相似文献
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Shake table investigation on the seismic performance of hospital equipment supported on wheels/casters 下载免费PDF全文
下载免费PDF全文 This paper presents an experimental investigation on the seismic response of medical equipment supported on wheels and/or casters. Two pieces of equipment were tested: a large ultrasound machine and a cart carrying smaller medical equipment. In the first phase, the resistance of the wheels and casters of the equipment was characterized through a controlled‐displacement procedure on the shake table. In the second phase, an extensive shake table test program was carried out to investigate the seismic response of the equipment. The input signals for the shake table tests included floor motions of a four‐story steel braced‐frame hospital designed to satisfy seismic requirements of a site in the Los Angeles area. The results of 96 shake table tests reported in this study include the seismic performance of the equipment under both unlocked and locked conditions, located on various floor levels of the building. It was observed that engaging the casters' locking mechanism does not necessarily decrease the relative displacement. The displacement response was sensitive to the excitation intensity and the orientation of the equipment with respect to the input excitation. Based on the experimental observations, appropriate structural engineering demand parameters associated with the relative displacement and relative velocity demands of the equipment are proposed and used to develop conditional probability curves. Finally, in an effort to extend the results of this experimental study to similar equipment on wheels/casters, the performance of a simple numerical model in predicting the peak seismic demands is evaluated. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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The overturning fragilities of symmetric and asymmetric freestanding blocks, ranging in height from 0.54 to 3.6 m and with height‐to‐width ratios ranging from 2.1 to 6.6, are determined numerically. A probabilistic formulation regularizes the overturning responses when exposed to earthquake‐like random‐vibration waveforms. The peak amplitude of the forcing excitation (peak ground acceleration or PGA) is parameterized as a function of the block size, block shape, overturning probability, and either the PGA normalized peak ground velocity (PGV/PGA), spectral acceleration at 1 s (Sa(1)/PGA), or spectral acceleration at 2 s (Sa(2)/PGA). These later intensity measures are correlated with the duration of the predominant acceleration pulse. The overturning fragilities are compared with shake table experiments using blocks ranging in height from ～0.2 to 1.2 m and with height‐to‐width ratios ranging from ～2 to 10. Excitations utilized in the shake table experiments include recordings of the 1979 Imperial Valley, 1985 Michoacan, 1999 Duzce, 1999 Chi‐Chi, and 2002 Denali Earthquakes along with synthetic waveforms. The overturning fragilities accurately represent the overturning responses of blocks with simple basal contact conditions. Objects with multiple rocking points, such as precariously balanced rocks, are more fragile than predicted. Nondestructive tilting tests are used to account for blocks with complex basal contact conditions, demonstrating that these blocks overturn similarly to more slender blocks with simple contact conditions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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The performance of a well-designed layer of sand, and composites like layer of sand mixed with shredded rubber tire(RSM) as low cost base isolators, is studied in shake table tests in the laboratory. The building foundation is modeled by a 200 mm by 200 mm and 40 mm thick rigid plexi-glass block. The block is placed in the middle of a 1m by 1m tank filled with sand. The selected base isolator is placed between the block and the sand foundation. Accelerometers are placed on top of the footing and foundation sand layer. The displacement of the footing is also measured by LVDT. The whole setup is mounted on a shake table and subjected to sinusoidal motions with varying amplitude and frequency. Sand is found to be effective only at very high amplitude( 0.65 g) of motions. The performance of a composite consisting of sand and 50% shredded rubber tire placed under the footing is found to be most promising as a low-cost effective base isolator. 相似文献